Elastic rings that are inserted into inner grooves in workpieces are usually embodied from an elastomer and used as sealing rings. They usually have a diameter/thickness ratio of >10 and usually also a hardness <70 Shore. However, the invention is not limited to these values, these values do however define ranges in which the elastic rings are particularly unstable and consequently it is difficult to insert said elastic rings automatically into an inner groove in an automated manner. O-rings are the most frequent type of these sealing rings. Rings that have sealing lips are even more difficult to install since the lips themselves are extremely unstable and make it more difficult to perform the installation procedure in an automated manner.
In order to make it possible to install the elastic rings into the inner grooves, said elastic rings must first be deformed and must either be pulled or pushed into the workpiece opening in the region of the groove. The term “pulling” a ring is used if the cord forming the ring is subject to tensile stress and the term “pushing” is used if the cord is subjected to a compression load. A problem arises when inserting the ring into the groove if the ring lies in the region of the groove but must then be pushed into the groove along the complete circumference. In this case, the ring is compressed, which means that the compression load on the cord leads to the cross-section of the cord being increased in particular regions. This is detrimental for the positioning of the ring in the groove itself. Forces occur that produce uncontrollable deformations of the ring and can lead to the ring becoming damaged as it is inserted into the groove. In particular the friction forces between the ring and the workpiece, the extent of the compression, but also the fluctuating qualities of the rings with regard to their material, their surface quality and their hardness result in the compression of the rings making it extremely difficult to perform the installation procedure in an automated manner.
DE 37 10 829 A1 discloses a device for installing sealing rings, wherein a tool is placed on the workpiece and an axially displaceable finger grasps the sealing ring at a site on its circumference and then pulls said sealing ring into a transition sleeve, the inner cross-section of which corresponds to the inner cross-section of the workpiece opening. The ring is deformed into an oval that lies in an inclined manner in the sleeve. If the retaining region of the ring on which the finger is engaging has arrived at the groove, this retaining region is pushed into the groove by means of a rocking movement at the finger. A trailing slider then pushes the rest of the ring in the direction towards the groove so that said ring can then slide into the groove. It must also be possible for the ring to slide in the bottom of the groove so as to perform compensating movements which could be more difficult as a result of the high friction in the region of the bottom of the groove. Sliding means in particular in the form of oil is intended to reduce problems and can reduce problems. The known device is widely used in practice.
Furthermore, there are however alternative solutions that use a completely different technique. In this case, the ring is compressed in the ring plane (radial plane with regard to the non-deformed state) so that the ring diameter is reduced in size. In so doing, the ring must be retained between two plates since said ring is not to bulge out of the plane. DE 43 19 442 A1 discloses a corresponding compression drawer. In this case, the ring is compressed radially so uniformly inwards that it retains its circular shape. The ring must then be retained between two planar surfaces and inserted into the workpiece opening. As soon as the ring has arrived at the groove, the ring can relax and as a result of its intrinsic stress jump into the groove. This method has particular limits with regard to the dimensions and rigidity values of the rings since a high degree of compression is required.
If it is not possible to achieve this degree of compression, other installation variants can be used, wherein the ring likewise remains in its plane and is deformed only in the plane. By way of example, it is feasible to push the ring radially from one side inwards so that it assumes a kidney shape. Further other ideas also provide to push the ring with multiple fingers inwards in the ring plane in order to provide the ring with a clover leaf shape. As a result of its elasticity and intrinsic rigidity, the ring upon arriving at the groove jumps into the groove in a uniform as possible manner over the entire circumference in the case of all these variants.
It is the object of the invention to provide a device, a modular construction system and a method for inserting an elastic ring, in particular a sealing ring, into an inner groove of a workpiece opening and said device, modular construction system and method are to be extremely process-reliable and universally useable with respect to the geometric and material characteristics of the ring and also with respect to the geometries and dimensions of the ring in relation to the dimensions of the groove and the workpiece opening. It is namely necessary in the prior art to match the device very precisely to the specific ring and the workpiece.